US2329834A - Treatment of hydrocarbons - Google Patents

Description

Y Sept. 21, 1943. H. L. HAYS TREATMENT OF HYDROCARBONS Filed Sept. 2, 1941 I N .T w 0L IL 5 I 6 E mu 4 mm m l I H V M A M R 00 L EN V0 m5 R R A H 3 2 3 0 EOF ZO .U EI. Y 0 I! v. 3 9 '5 E 2 5 9 0 M 1.: 5 6 2 m \u 6 M 5 I .R I 4 w ll 7 5 a EY Patented Sept. 21, 1943 UNITED STATES PATENT OFFICE aszasss TREATMENT OF HYDROCABBONS Harrison L. Hays, Bartles ville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware application September 2, 1941, Serial No. 409,283 Claims. v(c1. 196-28) This invention relates to the manufacture of higher octane number hydrocarbons from lower octane number hydrocarbons and in particular to the manufacture of aviation and/or motor fuels of high octane number from a charge stock which may contain any combination of the hydrocarcarbons, such as the paraflln series, the various individual hydrocarbons differ widely among themselves as to detonation or combustion characteristics. This is exemplified by the detonation properties of normal hexane and 2,2-dimethyl butane (neohexane). Normal hexane, a straight chain hydrocarbon, is known to have an octane number of .59, whereas its isomer 2,2-dimethyl butane or neohexane, a hydrocarbon with a highly branched molecular structure, is generally known to have an octane number rating of 05.

The principal object of this invention is to produce higher octane number normally liquid hydrocarbons from lower octane number normally liquid hydrocarbons such as those found in natural gasoline stocks.

Another object is to produce higher octane number hydrocarbons suitable for use either directly as aviation or motor fuels, or as preparatory materials therefor, utilizing a charge stock which comprise any combination of the hydrocarbons in the natural gasoline range in any concentration whatsoever. 7

Further objects and advantages of this invention will become apparent as the following description and disclosure proceeds.

A number of methods have been proposed for the manufacture of higher octane number hy-' drocarbons from those of lower octane number, such asare' utilized in the production of lsooctane from isojbutane and other hydrocarbons'by various thermal and catalytic means, etc. However, by means of the present invention, through the use of satisfactory catalysts and'suitably selected conditions of temperature and pressure, a feed stock which contains any of the hydrocarbons in the natural gasoline range may be. made to react to produce other hydrocarbons of higher octane number suitable for use as or in the of aviation fuels and/or motor fuels.

preparation among the members of any one series of hydro- According to this invention, a natural gasoline feed stock, as heretofore described, is, in'the initial step of the process, subjected to catalytic desulfurization wherein pressures and temperatures used are of the order of 0 to 100 pounds per. square inch and 500 to-800 F., respectively. A suitable catalyst is employed, such as bauxite impregnated with sodium hydroxide. Conditions are maintained such that decomposition reactions are slight, and less than 5 per cent and preferably less than 2 per cent of the charge stock undergoes splitting reactions. Desulfurization is so conducted that the desulfurization product contains less than about 0.1% of sulfur and preferably less than about 0.01% of sulfur. Actually, pressures and temperatures of the order of 0 to 50 pounds per square inch and- 500 to 700 F..- respectively, seem to be preferable in promoting the desulfurization reaction in order to suppress more than slight decomposition. Suitable means of separation are now employed, wherein desulfurized hydrocarbons in the aviation fuel range of molecular weights are separated from those of higher molecular weight which are of motor fuel I.

grade. Prior to fractionation, a portion ofthe total liquid may be recycled to the desulfurization step for the purpose of control.

The fraction of aviation fuel range of molecular weight is subjected in the presence of a suitable isomerization catalyst such as one of the metallic halides, particularly aluminum chloride carried on a satisfactory supporting material and in the presence of hydrogen chloride, to reaction pressure and temperature conditions of the order of 0 to 500 or more pounds per square inch and 0 to 1000 respectively. These conditions are maintained such that decomposition reactions are slight, and less thanlO per cent, andpreferably less than 5 percent of the charge stock undergoes splitting reactions. The isomerization reaction is favored considerably if the temperatures which are used in coniunctlon'with a reasonably high pressure are maintained well below those at which appreciable decomposition usually begins. Therefore, pressures and temperatures of the order of to 300 pounds per square inch and 200 to 700 F., respectively, seem to be pro!- erable in promoting the isomerization reaction to be employed in this step of the proces Following suitable .means of separating the fraction of aviation grade from the isomerization product, the fraction of heavier material which is formed during the isomerization reaction is fed to the dehydrogenation step of the process to-.

gether with hydrocarbons of motor fuel grade from the desulfurization step. This combined 8 into a suitable catalyst case feed together with insuiliciently reacted recycle stock from a later stage in the process is subjected in the presence of a suitable catalyst, such as chromic oxide gel, chromic oxide carried on a suitable support, or bauxite, to reaction pressure and temperature conditions of the order of to 100 pounds or more per square inch and 600 to 1200 F., respectively. These conditions are maintained such that not more than 30 per cent or the total feed is converted per pass through the reaction zone, The suitable exact conditions depend upon the type of feed stock and the catalyst used and are best determined by trial. Separation steps are now employed which result in the isolation of the hydrocarbons in the motor fuel range from those both lighter and heavier. The process of this'invention may be carried out in equipment such as that illustrated diagrammatically in the drawing, which portrays one means by which the process may be practiced. Referring to the drawing in detail, a natural gasoline feed stock as heretofore described is in-. troduced via supply line I, tank 2, and conduit 3, together with recycle stock coming from sepa rators i0 and 13 by way of conduit l8, under suitable pressure to heating coil 4 enclosed in a suitable furnace or heating means 5. The preheated hydrocarbons then pass through conduit I, where they are subjected to the influence of a suitable catalyst such as bauxite impregnated with sodium hydroxide. The reaction temperatureis such that the decomposition of the hydrocarbons so treated will be not more than 2 per cent by weight for contact periods which may vary from one to two liquid volumes of feed per hour per volume of catalyst, the most suitable exact conditions being determined by trial. q

Following passage through the reaction zone the hot reaction products exchange .heat with the cold feed to the isomerization system in heat exchanger 9. Thence they pass via conduit 8 into a cooler where they are lowered to a suitable temperature prior to entry into separation element ill. Here a rough separation is made between components of aviation grade and heavier and lighter components. The aviation and heavier hydrocarbons pass via conduit ii into separation element ii. The lighterv components, which, due to the rough separation, may contain desirable components, are pumped via conduit l2 through suitable cooling and condensing means into separation element 13. Thence the light, undesirable components are removed from the system through conduit M. The pressure in element i3 is such that the condensate therein comprises the major portion of the desirable components in the overhead stream from element iii. The condensate in i3 passes out, via conduit i5 and joins the normal feed to separation element H which is passing through conduit Ii. For control,- a portion of the feed to element l'l may be recycled to tank 2 via conduit i6. A separation is secured in element i! such that the desirable lighter'components of essentially aviation grade molecular weight pass through conduit 18 in which they are cooled and condensed into condensate accumulator IS. A portion of the condensate in accumulator I9 is compressed to a sufliciently high pressure and is introduced condensate in i9 from the system for use as or in the blending of aviation gasoline, should such withdrawal be desired, conduit 2i is provided in communication with conduit 22. The condensate in excess of that required for refluxing and withdrawal as aviation fuel comprises the feed to the isomerization step.

The raw feed to the isomerization step passes via conduit 22, together with recycle stock from conduit 41, into isomerization feed surge tank 23. From 23 the total feed passes via conduit 24, dur ing which it is compressed to a; suitable isomerization reaction pressure of between 0 and 500 or more pounds per square inch, through heat exchanger 9, where it exchanges heat with the hot desulfurization catalyst chamber eiliuent in order to obtain a satisfactory isomerization reaction temperature. Conduit 25 provides a by-pass around heat exchanger 8 through which a portion of the isomerization feed may be passed for the purpose of controlling its temperature. The

preheated feed stockthen passes, together with light hydrocarbon vapors and hydrogen chloride recycle via conduit 48, into a suitable isomerization catalyst case 28. In the catalyst case 24 the gasoline hydrocarbons are subjected to the influence of asuitable catalyst, such as one of the metallic halides, aluminum chloride, for example. Instead of aluminum chloride, other.

amphoteric metal halides capable of acting as isomerization catalysts may be employed. Prefer ably, an aluminum halide is used, such as aluminum chloride or aluminum bromide, etc. The reaction'temperature is so regulated that the decomposition of the hydrocarbons so treatedwill be less than 5 per cent by weight for reaction periods which may vary from about 5 to 30 minutes, the most suitable exact conditions being determined by trial. Conditions may be maintained to vary the composition or the equilibrium mixture of reaction products in accordance with the type of product desired. The hydrogen halide employed in this isomerization step preferably corresponds to the metallic halide isomerization catalyst. The hydrogen halide serves to activate the isomerization catalyst. Following passage through the reaction zone, the hot reaction products pass via conduit 21 into a suitable cooler 28 where they are cooled by suitable means prior to being pumped into separation element 30. vConduit 29 comprises a by-' "pass around cooler 28 for the purpose of term as a reflux or cooling medium near the top of i1 perature control. Hydrocarbons lighter than those desired in aviation fuel, together with hydrogen chloride, pass through conduit II, in which they are cooled and condensed, into condensate accumulator 32. A portion of the condensate from accumulator 32 is compressed to a pressure sufllciently high to permit its introduction as a reflux or cooling medium near the top of element 30 via conduit 33. The condensed portion in excess of that required for this purpose is continuously'removed from the system as a liquid through conduit 34. The uncondensed portion which contains propane and lighter hydrocarbons and an appreciable concentration of hydrogen chloride is removed as a vapor near the top of element 32 and passes via conduit 48 to its point of juncture with the hot isomerization catalyst chamber feed in conduit 24. This material is recycled only because of its hydrogen chloride content.' If operating conditions render it desirable, a portion of this uncondensed material may be vented from conduit 48 by suitable venting means. A pump 49 may be provided in conduit for compressing the returned mate rial depending upon the desired operating pressure of the isomerization catalyst case 26; Fresh hydrogen chloride make-up is provided by hydrogen chloride gas storage tank 50.

The bottom product from separation element 30, which contains the, valuable aviation fraction, together with insufficiently reacted material and some heavier hydrocarbons which were formed in the reaction zone, passes via conduit 35 through a neutralization contactor 36 where a material such as an aqueous caustic soda solution is employed for the purpose of neutralizing or removing the small quantity of hydrogen chloride contained therein, Thence the hydrocarbons and neutralizing solution pass into a settling tank 31 where the hydrocarbons are separated from the neutralizing solution and pass via conduit 4| into separation element 42. The partially used neutralization solution which is recovered in settling tank 31 may be recirculated via conduit 38. Fresh neutralizing solution is introduced via conduit 39 and spent solution is withdrawn from the system via conduit 40.

The aviation fuel constituent from separation element 42 passes via conduit 43, in which it is cooled and condensed, into condensate accumulator 44. As in the preceding separation step, a

portion of this condensate is compressed and in troduced via conduit 45 near the top of element 42 to act as a reflux or cooling medium. The valuable constituent in excess of the amount required for refluxing purposes is removed from the system via conduit 46. This material may serve as, or be employed in the blending of, aviation gasoline. A portion of this material, however, is recycled to the system via conduit 41 for reaction control. The bottom product from ele-'- ment 42, which comprises hydrocarbons of higher molecular weight, passes via conduit-5i, together with dehydrogenation raw feed from the of the order of 600 to 800 F. prior to entry into exchanger 56, where they are further cooled by heat interchange with the total cold feed as heretofore described. Thence they are additionally cooled and passed into separation element 62. Hydrogen and lighter hydrocarbons,,togeth- I er with some of the heavier hydrocarbons, pass overhead via conduit 63, in which they are passes via conduit 66 in. which it is compressed to a pressure sufficiently high to permit its entry, together with the bottom product from separation element 64, into separation element 61. Hydrocarbons which are essentially butane in composition pass overhead via conduit 68, and are cooled, condensed and passed into condensate accumulator 69, A portion of the condensate in 69 is introduced near the top of 61 as a reflux or cooling medium via conduct 10, in which it is compressed. sufficiently. The quantity in excess of that required for refluxing is continuously withdrawn from the system through conduit 1| and comprises essentially butane. The bottom product from'separation element 61 passes through conduit 12 into separation element 13 where the motor fuel fraction is isolated from hydrocarbons of higher molecular weight. The motor fuel fraction passes through conduit 14, in which it is cooled and desulfurization system which is passing via conpressure between 0 and 100 or more pounds per square inch, through heat exchanger 56 where a certain temperature is; obtained by heat interchange with catalyst chamber eflluent products which are passing through conduit 60. Prior to condensed, into condensate accumulator 15; A

portion of the condensate is taken from accu' mulator 15 through conduit 16 and compressed to a pressure sufiiciently high, and introduced as via conduit 11. However, it is considered to be necessary to recycle a portion of this material via conduit 54 for process control, particularly to v control the quality and yield of desirable materials.

entry into the heat exchanger, the liquid feed is mixed with hydrogen and light hydrocarbon vaa suitable dehydrogenation catalyst case 59 The preheated hydrocarbons (600 to 1200 F.) then pass via conduit 58 into where they are subjected to the influence of a sponding to flow rates which may vary from 1%:

to 3 volumes of liquid feed per volume of catalyst per hour, most suitable exact conditions bein determined by trial.

Following passage through the reaction zone the hot reaction products pass via conduit 60 in which they are cooled by a suitable means from the reaction temperature down to a temperature The advantages of the process of the present invention are numerous. The process greatly increases both the octane number and lead response of the hydrocarbons treated; Moreover it enables the ready and economical production of exceedingly high quality fuels of both aviation and 1 stock before catalytic isomerization and before. "catalytic dehydrogenation is peculiarly beneficial from the standpoint of the adverse eiiect of sul-.

fur upon the isomerization and dehydrogenation catalysts even in concentrations as low as 0.004

per cent. The present invention allows the ready maintenance of total sulfur content of the feed atv a value suflicientiy low to insure an economic catalyst life. Moreover the process is advantageous in that it allows the use of ordinary carbon steel in the fabrication of the equipment,

particularly in that portion of the apparatus employed after the desulfurization step, except in operating zones where temperatures of 1000 F.

or higher compel the use of alloy steels of adequate creep stress characteristics. It has been tion this difflculty is readily overcome. Accordingly, the apparatus used in carrying out the process may be inexpensively constructed and has a longer useful life, and the. necessity for frequent shutdown of the plant due to corrosion is eliminated.

Another advantage is that, using the process of the present invention, it is not necessary to carry the entire charge through the three major steps, but on the contrary the aviation portion of the isomerization product is adapted directly for use-as a superior aviation fuel. The heavy portion of the isomerization product has been largely isomerized to branch chain hydrocarbons and thereby converted to a form where, upon dehydrogenation, it yields a superior motor fuel. With the process of the present invention the heavy portion of the desulfurizatioh product is not subjected to the isomerization step, but goes directly to the dehydrogenation step, which is further advantageous. In addition the process is' capable of a high degree of flexibility of operation and of ready control to meet the needs of the original charge stock and the existing demand. The process yields a maximum of premium products from the charge stock at hand in and a heavier fraction, combining said heavier fractions, subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

3. A process of producing high octane number hydrocarbons which comprises subjecting relatively low octane number natural gasoline charge stoclr to catalytic desulfurization, separating the Product to recover a fraction in the aviation fuel range of molecular weights and a heavier fraction, subjecting said first-named fraction to catalytic isomerization, separating the product to recover a fraction suitable as aviation gasoline and a heavier fraction, combiningsaid heavier fractions, subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

4. A process of producing high octane number hydrocarbons from relatively low octane number hydrocarbons which comprises subjecting. relatively low octane number hydrocarbon charge stools to catalytic desuli'urization by passing it undera pressure of from 0 to about 50 pounds per square inch and at a temperature of from about 500 to about 700 F. in contact with a catalyst of bauxite impregnated with sodium hydroxide under conditions such that less than about 2 per cent of the charge stock undergoes splitting reactions during the dsulfurization I step, separating the product to recover a fraction in the aviation fuel range of molecular weights and a heavier fraction, subjecting said a conveniently controlled economical manner. v

Moreover the several steps oithe process are so inter-related with respect to each other as to give unusual facility ofoperation and a high degree of operating efliciency.

It will be understood that the embodiment described herein, while representing the preferred practice of my invention now known to me, is merely illustrative of the inventive thought, and that the invention is to be taken as limited only by the spirit andterms of the appended claims.

I claim: 1. A procm of producing high octane aviation and motor fuel fromrelatively low octane numbar hydrocarbons which comprises'subjecting low octane number natural gasoline charge stock to tion product to recover therefrom a lighter frac-' tion suitable as aviation gasoline and a heavier fraction, subjecting a feed comprising the whole of said heavier fraction to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

2. A process of producing high octane number hydrocarbons from. relatively low octane number hydrocarbons which comprises subjecting relatively low octane number hydrocarbon charge stock to catalytic desulfurization, separating the product to recover a fraction in the aviation fuel range of molecular weights and a heavier fraction, subjecting said first-named fraction to catalytic isomerization, separating the product to recover a fraction suitable as aviation gasoline 1 I first-named fraction to catalytic isomerization, separating the product to recover a fraction suitable as aviation gasoline and a heavier fraction, combining said heavier fractions, subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

5. A process of producing high octane number hydrocarbons from relatively low octane number hydrocarbons which comprises subjecting relatively low octane number hydrocarbon charge stock to catalytic desulfurizaticn, separating the product to recover a fraction in the aviation fuel range of molecular weights and a heavier fraction, subjecting said first-named fraction to catalytic isomerization in the presence of a metallic halide, separating the product to recover'a fraction suitable as aviation gasoline and a heavier fraction. combinmg said heavier fractions, subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

8. A process of producing high octane number hydrocarbons from relatively low octane mnnber hydrocarbons which comprises subjecting. relatively low octane number hydrocarbon charge stock to catalytic desulfurization, separating the product to recover a fraction in the aviation fuel, range of molecular weights and a heavier'fraction, subjecting said first-named fraction to catalytic isomerizationin the presence of aluminum chloride and in the presence of hydrogen chloride, separating theproduct to recover a fraction suitable as aviation gasoline and a heavier fraction, combining said heavier fractions. subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenate'd product. i

7. A process of producing high octane number hydrocarbons from relatively low octane number hydrocarbons which comprises subjecting rela- 9. A process 6:- producinghigh octane number tively low octane .number' hydrocarbon charge stock to catalytic desulfurization, separating the product to recover a fraction in the aviation fuel range of molecular weights and a heavier-trac tion, subjecting said first-named fraction to datalytic isomerization under a pressure of from about 50 to about 300 pounds per square inch and at a temperature of from about 200 toabout 700 F. in the presence of aluminum chloride and in the presence of hydrogen chloride under such conditions that less than about 5 per cent of the feed undergoes splitting during the isomerization step, separating the product to recover a fraction suitable as aviation gasoline and a heavier fraction,- combining said heavier fractions, subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

8. A process of producing high octane number hydrocarbons from relatively low octane number hydrocarbons which comprises subjecting relatively low octane number hydrocarbon charge stock to catalytic desulfurization, separating the product to recover a fraction in the aviation fuel range of molecular weights and a heavier fraction, subjecting said first-named fraction to catalytic isomerization, separating the product to recover a fraction suitable as aviation gasoline and a heavier fraction, combining said heavier fractions,subjecting said combined fractions to catalytic dehydrogenation by passing same under a pressure of from to about 100 pounds per square inch and at a temperature of from about 600 to about 1200 F. in contact with a dehydrogenation catalyst selected from the group conmic oxide and bauxite, under conditions such that not more than about 30 per cent of the tothe dehydrogenated product.

hydrocarbons from relatively low octane number hydrocarbons which comprises subjecting relatively low octane number hydrocarbon charge stock to catalytic desulfurization, separating the product to recover a fraction in the aviation fuel range of molecular weights and a heavier fraction, subjecting said first-named-fraction to-catalytic isomerization in the presence of a metallic chloride and in the presence of hydrogen chloride,

. separating the isomerlzation product into a first tion,

fraction comprising those suitable for use in aviation fuel together with hydrogen chloride, a second fraction suitable as aviation gasoline, and a heavier fracrecycling said first fraction containing hydrogen chloride to th i'somerization feed, combining said heavier fractions, subjecting said combined fractions to catalytic dehydrogenation, and recovering high octane number motor fuel from the dehydrogenated product.

10. A process of producing high octane number hydrocarbons from relatively low octane number sisting of chromic oxide gel, supported chov hydrocarbons which comprises subjecting relatively low octane number hydrocarbon charge stock to catalytic desulfurization, separating the product to recover a fraction in the aviation fuel 'range of molecular weights and a, heavier fraction, subjecting said first-named fraction to catalytic isomerization, separating the product to recover a fraction suitable as aviation gasoline and a heavier fraction, combining said heavier-fractions, subjecting said combined fractions to catalytic dehydrogenation, separating the dehydrogenation product into a fraction of high octane number hydrocarbons of motor, fuel grade and into a fraction containing hydrogen, and recycling at'least a portion of said last-named hydrogen-containing fraction to the dehydrogenation step. e

" HARRISON L. HAYS.

hydrocarbons lighter than

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